20. Current Coupled Coils

Two solenoid coils connected by wires are arranged so that magnets on springs oscillate in them. When one magnet is set oscillating, the induced current causes the other to oscillate also.

In a variation of this demonstration known as Nefkens's Telephone the two coils are set on opposite sides of the lecture hall with a long wire connecting them. Just by arranging some pieces of iron and copper in the right way, movement here causes movement over there -- an astonishing achievement of the mind of Man.

Short the leads of one of the coils and the oscillation of the magnets will be rapidly damped out by Lenz's Law.